title: Influence of immunoglobulin light chain dimers on the results of the quantitative nephelometric assay.
abstract: BACKGROUND
  Some polymeric forms of immunoglobulin free light chains (FLCs) have been identified, such as dimer, trimer and tetramer, and the quantitative nephelometric assay of kappa and lambda light chains is very important to the diagnosis and management of multiple myeloma (MM), primary systemic amyloidosis (AL), etc. But, whether polymeric molecules could affect the results of the nephelometric assay, is rarely reported.
  
  
  METHODS
  12 urinary samples from patients with light-chain MM were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and every sample was run with reduced and nonreduced sample buffer in one gel. Urinary kappa and lambda light chains were measured on the BNII nephelometer. We then added 3 microL beta-mercaptoethanol (2-ME) to the samples to transform the dimers into monomeric forms and measured them again.
  
  
  RESULTS
  10 samples showed obvious dimers by SDS-PAGE, of which 2 samples were kappa light chain dimers. Six samples had decreased quantitative results contrasted with the former values. The two samples of kappa light chain dimers decreased more obviously.
  
  
  CONCLUSIONS
  The light chain dimer combined with more antibodies than the monomer and a larger antigen-antibody complex was formed. The larger complex could magnify the reaction between antigen and antibody of the nephelometric assay and therefore false elevated results could measured.
authors.affiliation: Department of Laboratory Medicine, Shanghai Changzheng Hospital, Second Military Medical University & Clinical Immunology Center of PLA, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Li
authors.forename: Honglian
authors.initials: H
authors.lastname: Geng
authors.forename: Zaixing
authors.initials: Z
authors.lastname: Yang
authors.forename: Renqian
authors.initials: R
authors.lastname: Zhong
mesh_terms: D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000652:urine*; D007146:Immunoglobulin lambda-Chains / Q000652:urine*; D009391:Nephelometry and Turbidimetry; D010084:Oxidation-Reduction
chemical_list: D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains